The present invention relates to a solid resin-coated magnet powder for producing an improved anisotropic bonded magnet, and a method of producing the magnet.
An anisotropic bonded magnet as disclosed, for example, in Japanese Patent Laid-Open No. 1-281707, is conventionally formed by kneading an anisotropic magnet powder with a solid resin such as a solid epoxy resin, a polyester resin, a phenolic resin or the like, granulating the resultant mixture to form solid resin coated particles, press-molding the solid resin-coated magnet powder in a magnetic field to form a molded product, and curing the solid resin by heating the molded product. The use of a solid resin-coated magnet powder is considered be superior to one which is liquid coated because it has better fluidity, and can thus be cast to form a thinner product.
Referring to FIG. 3, an anisotropic bonded magnet produced by the above conventional method mainly consists of a solid resin-coated composite magnet powder 5 containing a plurality of anisotropic magnet powder particles 1 coated with a solid resin 2. Even if each of the individual anisotropic magnet powder particles 1 has a high degree of anisotropy, the plurality of the anisotropic magnet powder particles 1 collectively exhibit random orientation directions 4. Thus, the solid resin-coated composite magnet powder 5 has insufficient anisotropy as a whole, and cannot be oriented to exhibit sufficient anisotropy when molded in a magnetic field to produce a magnet. As a result, the anisotropic bonded magnet produced by the prior-art method has generally poor magnetic characteristics. There is also the problem that a molded product using the conventional solid resin-coated composite magnet powder 5 has a lower density than that of a molded product of liquid resin-coated magnet powder produced using the same molding pressure.